Various instruments such as a controller, a temperature instrument, a recorder, etc. which are set and used for a long period of time in the same production facilities of a plant need periodic checks for keeping quality of produced goods. Since such production facilities are used for more than ten years, it is important to retain and administrate the check data. For the instrument check system, there is a technical disclosure in JP 2005-84941 A.
FIG. 4 is a functional block diagram showing a configuration of a conventional instrument check system applying to a controller by way of example. A controller to be operated in a plant has an input terminal 11 for receiving a measurement value PV of a sensor 2 applied as a voltage value and an output terminal 12 for outputting an operation value MV serving as a voltage value to a control valve 3.
Although not illustrated in FIG. 4, there is another input terminal for receiving a set value. Although one input terminal 11 and one output terminal 12 were illustrated for brevity of explanation, there are provided a plurality of input and output terminals, if need be.
In a steady-state control mode, the measurement value PV applied to the input terminal 11 is converted into a digital value by an AD converter 13, and is inputted to a control arithmetic section 14 via a switch S1 which is switched over when check is implemented.
The control arithmetic section 14 controls and operates the deviation between the measurement value PV and a set value to be inputted, although not illustrated, and delivers the resultant arithmetic value to a DA converter 15, via a switch S2 which is switched over when check is implemented, where the arithmetic value is converted into a voltage value, which is applied to a control valve 3 via an output terminal 12 as an operation value MV.
In a check mode, the input terminal 11 and the output terminal 12 are severed from the sensor 2 and the control valve 3. Instead, a set voltage value Vi of a voltage generation unit 41 of a tool 4 for use in checking (hereinafter referred to checking tool 4) is inputted to the input terminal 11, while a voltage value Vo′ generated in the output terminal 12 is read by a voltage measurement unit 42 of the checking tool 4.
A set operation of the voltage generation unit 41 and read operation of the voltage measurement unit 42 are implemented by an operator 5 who is in charge of checking. In the check mode, the operator 5 switches over the switches 1 and 2 by an operation section 16 provided in the controller 1, and severs the input and the output of the control arithmetic section 14 from the AD converter 13 and the DA converter 15.
An output Vi′ of the AD converter 13 is inputted to and displayed on a display section 17 provided in the controller 1 via the switch S1, and its display data is read by the operator 5. Further, an output checking voltage Vo, which is generated in a compulsory output section 18 provided in the controller 1 based on an instruction from an operation section 16 to the compulsory output section 18 by the operator 5, is inputted to the DA converter 15 via the switch S2.
The voltage Vo′ to be generated in the output terminal 13 by the DA converter 15 for receiving the output checking voltage Vo is measured by the voltage measurement unit 42 of the checking tool 4, and the measurement data to be displayed is read by the operator 5.
The operator 5 self-determines as to whether set contents of the voltage generation unit 41 and the operation section 16, read values of the display data and the displayed data of the display section 17 and the voltage measurement unit 42 are within accuracy, respectively, and the result of self-determination is manually written in a check sheet 6. The check sheet 6 which is prepared for every periodic checking is retained for a long period of time over an operation period of the instrument as a storage check sheet 6′.
There are following problems in the conventional instrument check system.
(1) There is no stylized format in a paper check sheet so that a customer or an operator has prepared the check sheet by himself of herself. Accordingly, there is a possibility that omission of data occurs and ambiguity remains in a go/no-go check.
(2) Since the check data is paper media and is retained in a place different from the place where an instrument serving as a check object is kept, it is difficult to match between an instrument body and a check history.